Intravascular ultrasound (IVUS) imaging is a technology that permits tomographic visualization of a cross section through the vessel wall, and is increasingly employed to assist in selecting and evaluating therapeutic intervention. In addition, there is a realization in the community that determining the composition of plaques may be equally or more important than their size. Recent work indicates that the erosion and rupture of vulnerable atherosclerotic plaque is the cause of most acute coronary syndromes. Vulnerable plaques are typically comprised of thin (<65 mu m) fibrous caps infiltrated with macrophages that encapsulate lipid-rich necrotic cores with adjacent microcalcificaton. In vivo identification of plaque size, geometry, and composition should enable the detection of vulnerable plaque before rupture. To this end, Volcano has developed an IVUS based spectral analysis technique called "VH IVUS(TM)" that can accurately determine plaque geometry and composition. However, standard clinical IVUS implementation is limited to approximately 100 mu m resolution and increasing both he axial and lateral resolution may improve further the accuracy of our VH IVUS(TM) technique in addition to increasing the overall quality of the IVUS image. Focused broadband ultrasonic transducers have increased axial and lateral resolution when compared to standard IVUS device, but are difficult to fabricate from ceramic materials using traditional manufacturing methods. We therefore intend to significantly improve the spatial resolution of IVUS by utilizing MEMS (microelectromechanical systems) based manufacturing methods and broadband transducer materials to fabricate transducers suitable for intracoronary application. This will result in a system capable of producing high-resolution images with an increased ability to identify plaque constituents and components. To accomplish this, we have formed a multidisciplinary team combining expertise in MEMS technology, IVUS catheter development, ultrasonics, and image processing. The transducer will be fabricated using MEMS techniques that are compatible with microelectronic fabrication, which will allow cost-effective production of an integrated transducer with electronics in a form factor that will be small enough for IVUS catheter implementation. [unreadable] [unreadable] [unreadable]